Paper feed apparatus

ABSTRACT

In one embodiment of the invention, in a paper feed apparatus having a half-moon roller disposed above a plurality of sheets of paper stored in a stacked manner, and an auxiliary roller provided along one end of a half-circumferential face of the half-moon roller, the half-moon roller being rotated in a state in which a topmost sheet of paper has been put in contact with a height regulating member due to the sheets of paper being biased upward, so that the auxiliary roller and the half-circumferential face of the half-moon roller are successively pushed against the topmost sheet of paper, and while the sheets of paper are pushed down by the auxiliary roller or the half-circumferential face of the half-moon roller, the topmost sheet of paper is pulled out by the half-circumferential face of the half-moon roller: the one end of the half-circumferential face of the half-moon roller is separated from the auxiliary roller, and a curvature of the one end of the half-circumferential face is gradually increased closer to the auxiliary roller.

BACKGROUND OF THE INVENTION

This application claims priority under 35 U.S.C. §119(a) on PatentApplication No. 2008-185078 filed in Japan on Jul. 16, 2008, the entirecontents of which are herein incorporated by reference.

The present invention relates to a paper feed apparatus that is appliedin an image forming apparatus such as a copier, a printer, or afacsimile apparatus, for example, and feeds recording paper or the like.

JP S62-191337A discloses this type of conventional paper feed apparatus.Here, a bottom plate on which a plurality of sheets of paper are storedin a stacked manner is biased upward, and the sheets of paper are storedin a state in which the topmost sheet of paper is abutted against aheight regulating member. A half-moon roller disposed above the sheetsof paper is rotated so that the half-circumferential face of thehalf-moon roller pushes against the topmost sheet of paper, and thetopmost sheet of paper is pulled out by the half-circumferential face ofthe half-moon roller.

Also, in the disclosure of JP H5-286585A, an auxiliary roller isadditionally provided at the end of the half-circumferential face of thehalf-moon roller. By rotating the half-moon roller, thehalf-circumferential face of the half-moon roller is pushed against thetopmost sheet of paper and the topmost sheet of paper is pulled out bythe half-circumferential face of the half-moon roller. When thehalf-circumferential face of the half-moon roller is separated from thetopmost sheet of paper, the auxiliary roller, which rotates togetherwith the half-moon roller, is pushed against the topmost sheet of paper,pushing down the sheets of paper.

There is also a conventional apparatus as shown in FIG. 7. In thisapparatus, an auxiliary roller 202 is provided in the vicinity of ahalf-circumferential face end 201a of a half-moon roller 201. As shownin FIG. 8, the half-moon roller 201 is rotated so that the auxiliaryroller 202 and the half-circumferential face of the half-moon roller 201successively push against a topmost sheet of paper 204, while the sheetsof paper are pushed down by the auxiliary roller 202 or thehalf-circumferential face of the half-moon roller 201 so that thetopmost sheet of paper 204 is separated downward from a heightregulating member 203, the topmost sheet of paper 204 is pulled out bythe half-circumferential face of the half-moon roller 201.

Various conventional apparatuses that employ a half-moon roller in thisway have been provided.

Incidentally, in the conventional apparatus in FIGS. 7 and 8, a 90degree corner is formed in the half-circumferential face end 201 a ofthe half-moon roller 201, and because the half-circumferential face end201 a drops precipitously, when the auxiliary roller 202 and thehalf-circumferential face of the half-moon roller 201 are successivelypushed against the topmost sheet of paper 204, the time during which theauxiliary roller 202 and the half-circumferential face of the half-moonroller 201 both are in contact with the topmost sheet of paper 204 isextremely short, and at about the same time that the auxiliary roller202 separates from the topmost sheet of paper 204, the corner of thehalf-circumferential face end 201 a of the half-moon roller 201 ispressed against the topmost sheet of paper 204. At this time, thetopmost sheet of paper 204 is static, and the topmost sheet of paper 204is locally pushed against by the corner of the half-circumferential faceend 201 a of the half-moon roller 201, and the static frictional forcebetween the topmost sheet of paper 204 and the sheet of paper below thesheet of paper 204 becomes very high. Therefore, paper multi-feedingoccurs in which when the topmost sheet of paper 204 is pulled out by thehalf-circumferential face of the half-moon roller 201, the sheet ofpaper below the sheet of paper 204 is also pulled out at the same time.

SUMMARY OF THE INVENTION

The present invention was made in consideration of the above problems,and it is an object thereof to provide a paper feed apparatus in whichpaper multi-feeding does not occur in a configuration in which anauxiliary roller is provided at an end of a half-circumferential face ofa half-moon roller.

In order to address the above problems, the invention provides a paperfeed apparatus having a half-moon roller disposed above a plurality ofsheets of paper stored in a stacked manner, and an auxiliary rollerprovided along one end of a half-circumferential face of the half-moonroller, the half-moon roller being rotated in a state in which a topmostsheet of paper has been put in contact with a height regulating memberdue to the sheets of paper being biased upward, so that the auxiliaryroller and the half-circumferential face of the half-moon roller aresuccessively pushed against the topmost sheet of paper, and while thesheets of paper are pushed down by the auxiliary roller or thehalf-circumferential face of the half-moon roller, the topmost sheet ofpaper is pulled out by the half-circumferential face of the half-moonroller: the one end of the half-circumferential face of the half-moonroller being separated from the auxiliary roller, and a curvature of theone end of the half-circumferential face being gradually increasedcloser to the auxiliary roller. Also, in the paper feed apparatus withthe above configuration, before the auxiliary roller separates from thesurface of the topmost sheet of paper, the one end of thehalf-circumferential face of the half-moon roller having a largecurvature presses against the surface of the topmost sheet of paper.Further, in the paper feed apparatus with the above configuration, thehalf-circumferential face of the half-moon roller is configured with africtional face. Furthermore, in the paper feed apparatus with the aboveconfiguration, the half-moon roller is configured from a frame body thathas been fixed to a shaft that serves as a rotational center of thehalf-moon roller, and a friction rubber that has been overlaid on thehalf-circumferential face of the frame body, the auxiliary roller beingrotatably linked to one end of the frame body, and thehalf-circumferential face of the half-moon roller is the outside surfaceof the friction rubber, and the one end of the half-circumferential faceof the half-moon roller is part of the friction rubber.

According to the invention having this sort of configuration, the oneend of the half-circumferential face of the half-moon roller isseparated from the auxiliary roller, and the curvature of the one end ofthe half-circumferential face is gradually increased closer to theauxiliary roller, so from before the auxiliary roller separates from thetopmost sheet of paper, the half-circumferential face end of thehalf-moon roller gradually starts to be pushed against the topmost sheetof paper, thus increasing the time that both the auxiliary roller andthe end of the half-circumferential face of the half-moon roller are incontact with the topmost sheet of paper. Therefore, the restoring forcein the upward direction of the sheets of paper is received in adispersed manner at the auxiliary roller and the end of thehalf-circumferential face of the half-moon roller, and the staticfrictional force between the topmost sheet of paper and the sheet ofpaper below the topmost sheet of paper decreases. In this state, pullingout of the topmost sheet of paper by the end of the half-circumferentialface of the half-moon roller is started, and only this topmost sheet ofpaper is quickly pulled out, so paper multi-feeding is unlikely tooccur.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view that shows an image forming apparatusin which one embodiment of a paper feed apparatus of the invention isapplied.

FIG. 2 is a cross-sectional view that shows the paper feed apparatus ofthis embodiment.

FIG. 3 is a cross-sectional view that shows an enlarged view of thevicinity of a half-moon roller in the paper feed apparatus in FIG. 2.

FIG. 4 is a cross-sectional view that shows a state in which thehalf-moon roller in the paper feed apparatus in FIG. 2 has rotatedapproximately 90 degrees in the counter-clockwise direction.

FIG. 5 is a cross-sectional view that shows a further enlarged view ofthe vicinity of one end of the half-moon roller and an auxiliary roller.

FIG. 6 shows a process of displacement of the surface of a topmost sheetof paper relative to the half-moon roller and the auxiliary roller.

FIG. 7 is a cross-sectional view that shows an enlarged view of thevicinity of a half-moon roller in a conventional paper feed apparatus.

FIG. 8 is a cross-sectional view that shows a state in which thehalf-moon roller in the paper feed apparatus in FIG. 7 has rotatedapproximately 90 degrees in the counter-clockwise direction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the invention will be described in detailwith reference to the attached drawings.

FIG. 1 is a schematic view that shows an image forming apparatus inwhich one embodiment of a paper feed apparatus of the invention isapplied. This image forming apparatus, acquires image data that has beenread from an original, or acquires image data that has been receivedfrom outside, and forms a monochrome image represented by this imagedata on paper. Broadly speaking, this configuration includes anautomatic document feeder (ADF) 101, an original reading apparatus 102,a printer unit 103, a paper transport unit 104, and a paper feedapparatus 105.

In the automatic document feeder 101, when an original of at least onesheet is placed on an original placement tray 11, the original is pulledout from the original placement tray 11 sheet by sheet and conveyed sothat this original is guided to and passed over a first glass platen 14of the original reading apparatus 102, and then the original isdischarged to a discharge tray 12.

In the original reading apparatus 102, an optical unit including a firstscanning unit 15 and a second scanning unit is disposed below the firstglass platen 14, and when the original passes over the first glassplaten 14, the original surface is exposed to light by a light source ofthe first scanning unit 15, reflected light from the original surface isguided to an imaging lens 17 by mirrors of the first scanning unit 15and the second scanning unit 16, and an image of the original surface isformed on a CCD (Charge Coupled Device) 18 by the imaging lens 17. TheCCD 18 repeatedly reads the image of the original surface in a mainscanning direction, and outputs image data that represents the image ofthe original surface.

Also, when an original has been placed on a second glass platen 19 onthe upper face of the original reading apparatus 102, while moving thefirst scanning unit 15 and the second scanning unit 16 in a sub-scanningdirection, the original surface on the second glass platen 19 is exposedto light by the first scanning unit 15, reflected light from theoriginal surface is further reflected and guided to the imaging lens 17by the first scanning unit 15 and the second scanning unit 16, and animage of the original surface is formed on the CCD 18 by the imaginglens 17. At this time, the first scanning unit 15 and the secondscanning unit 16 are moved while maintaining a predetermined speedrelative to each other, so that the positional relationship of the firstscanning unit 15 and the second scanning unit 16 is always maintainedsuch that the length of a light path of reflected light, i.e., from theoriginal surface to the first and second scanning units 15 and 16 to theimaging lens 17 to the CCD 18, does not change, and thus focus of theimage of the original surface on the CCD 18 is always preciselymaintained.

After a control circuit of a microcomputer or the like performs variousimage processing on the image data that has been output from the CCD 18,the image data is output to the printer unit 103.

Accordingly, in the original reading apparatus 102 of this embodiment,an original transport system in which an original is conveyed on thefirst glass platen 14, and an original fixed system in which an originalis placed on the second glass platen 19, and then the optical unit (thefirst scanning unit 15 and the second scanning unit 16) is moved, areboth employed.

A photosensitive drum 4 is disposed in approximately the middle of theprinter unit 103, and around the photosensitive drum 4 are disposed acharging unit 5, an optical scanning unit 6, a development unit 7, atransfer unit 8, and a cleaning unit 9.

The charging unit 5 uniformly charges the surface of the photosensitivedrum 4. The optical scanning unit 6 inputs image data, and whilemodulating the strength of an optical beam according to the image data,scans the optical beam on the uniformly charged photosensitive drum 4 towrite an electrostatic latent image on the photosensitive drum 4. Thedevelopment unit 7 develops the electrostatic latent image on thephotosensitive drum 4 using a developer, thus forming a developed imageon the photosensitive drum 4. The transfer unit 8, while conveying papersandwiched between the transfer unit 8 and the photosensitive drum 4,transfers the developed image on the photosensitive drum 4 onto paper.The cleaning unit 9 removes developer remaining on the photosensitivedrum 4, making it possible to form a new developed image on thephotosensitive drum 4.

A fixing apparatus 20 is disposed in the upper part of the printer unit103. The fixing apparatus 20 receives paper on which an image has beentransferred, and sandwiching that paper between a fixing roller and apressure roller, fixes the developed image that has been transferredonto the paper.

This paper is conveyed upward by a transport roller, and discharged to adischarge tray 22 from a discharge roller 21.

Also, when forming an image on both faces of paper, the paper isreverse-conveyed in the opposite direction by the discharge roller 21,and further conveyed to a reverse transport path 23, and after reversingthe front and back sides of that paper, the paper is again conveyed tothe printer unit 103, and a developed image is transferred and fixed tothe back side of that paper. Then the paper is discharged from thedischarge roller 21 to the discharge tray 22.

The paper feed apparatus 105 is provided with a paper feed cassette 24.Paper is separated and supplied sheet by sheet from the paper feedcassette 24, and supplied between the photosensitive drum 4 and thetransfer unit 8, where the developed image on the photosensitive drum 4is transferred to this paper.

Next is a detailed description of the paper feed apparatus 105 of thisembodiment with reference to FIG. 2. In this paper feed apparatus 105,the paper feed cassette 24 is supported so as to be capable of slidingto the front side of the body of the image forming apparatus. The paperfeed cassette 24 is pulled out to the front side, and a batch of paperis stored stacked on a bottom plate 31 inside of the paper feed cassette24. A rear edge regulating member 32 supported so as to be capable ofmoving left-right in FIG. 2 is provided on the floor of the paper feedcassette 24. The front edge of the paper batch on the bottom plate 31 isput in contact with an inner wall face 24 a of the paper feed cassette24, the rear edge regulating member 32 is moved until abutting againstthe rear edge of the paper batch on the bottom plate 31, and the paperbatch on the bottom plate 31 is positioned sandwiched between the innerwall face 24 a and the rear edge regulating member 32. Also, both sidesof the paper batch are positioned sandwiched by a pair of guide members(not shown) provided so as to be movable on the floor of the paper feedcassette 24.

Furthermore, the bottom plate 31 is axially supported by a shaft 31 a,and is biased in the counter-clockwise direction around the shaft 31 aby an unshown spring. The paper batch on the bottom plate 31 is raisedupward until a topmost sheet of paper 25 on the bottom plate 31 makescontact with a height regulating member 33.

A half-moon roller 34 is disposed above the front end side of the bottomplate 31 and is axially supported, and is driven so as to rotate in thecounter-clockwise direction around a shaft 35. An auxiliary roller 36 isadditionally provided at one end of the half-circumferential face of thehalf-moon roller 34.

When the half-moon roller 34 is driven so as to rotate in thecounter-clockwise direction, first the auxiliary roller 36 pressesagainst the topmost sheet of paper 25 on the bottom plate 31, and whilethe auxiliary roller 36 rolls on the topmost sheet of paper 25, thepaper batch on the bottom plate 31 is pushed downward against the springrestoring force, so that the topmost sheet of paper 25 is separateddownward from the height regulating member 33. Next, thehalf-circumferential face of the half-moon roller 34 presses against thetopmost sheet of paper 25, and the topmost sheet of paper 25 is pulledout by the half-circumferential face of the half-moon roller 34.

Similarly thereafter, each time that the half-moon roller 34 makes onerotation in the counter-clockwise direction, the topmost sheet of paper25 is pushed away from the height regulating member 33 by the auxiliaryroller 36, and the topmost sheet of paper 25 is pulled out by thehalf-circumferential face of the half-moon roller 34.

FIG. 3 is a cross-sectional view that shows an enlarged view of thevicinity of the half-moon roller 34. FIG. 4 is a cross-sectional viewthat shows a state in which the half-moon roller 34 has rotatedapproximately 90 degrees in the counter-clockwise direction. FIG. 5 is across-sectional view that shows a further enlarged view of the vicinityof one end of the half-moon roller 34 and the auxiliary roller 36.

The half-moon roller 34 as shown in FIGS. 3 to 5 includes a frame body41 and a friction rubber 42. The frame body 41 is fixed to the shaft 35,and the friction rubber 42 is overlaid on the half-circumferential faceof the frame body 41. Both ends 42a of the friction rubber 42 are fixedby hooking to respective engaging recesses 41 a on both sides of theframe body 41. The outside surface of the friction rubber 42 serves as ahalf-circumferential face 34 a of the half-moon roller 34, and part ofthe friction rubber 42 becomes one end 34 b of the half-circumferentialface 34 a.

The rotatable auxiliary roller 36 is linked to an end 41 b of the framebody 41 by an unshown linking structure, and the auxiliary roller 36 isdisposed separated from the end 34 b of the half-moon roller 34.

In FIG. 5, the half-circumferential face 34 a of the half-moon roller34, except for the one end 34 b of the half-circumferential face 34 a,traces a circular arc around the shaft 35 (shown in FIGS. 3 and 4).Also, an outermost circumferential position 36 p of the auxiliary roller36 is on a rotational trajectory S where the half-circumferential face34 a of the half-moon roller 34 rotates around the shaft 35, or in thevicinity of the rotational trajectory S.

Assuming that the one end 34 b (part of the friction rubber 42) of thehalf-circumferential face 34 a is a portion on the right side from aposition 34 p, the half-circumferential face 34 a traces a circular arcaround the shaft 35 on the left side from the position 34 p, and the oneend 34 b of the half-circumferential face 34 a is formed on the rightside from the position 34 p such that a curvature R of that circular arcgradually increases at positions closer to the auxiliary roller 36. Thusthe one end 34 b of the half-circumferential face 34 a is formed so asto be enveloped to the inside.

When this sort of half-moon roller 34 is rotationally driven in thecounter-clockwise direction together with the auxiliary roller 36, aspreviously described, the auxiliary roller 36 presses against a surface25 a of the topmost sheet of paper, and while the auxiliary roller 36rolls on the surface 25 a of the topmost sheet of paper, the paper batchon the bottom plate 31 is pushed downward against the spring restoringforce.

At this time, the topmost sheet of paper is biased upward to always bepressed against the half-moon roller 34 or the auxiliary roller 36, soas shown in FIG. 6, the half-moon roller 34 and the auxiliary roller 36are successively displaced relative to the surface 25 a of the topmostsheet of paper. In FIG. 6, the solid line indicates a state in whichonly the auxiliary roller 36 is pressed against the surface 25 a of thetopmost sheet of paper, the dotted line indicates a state in which theone end 34 b of the half-circumferential face 34 a of the half-moonroller 34 and the auxiliary roller 36 are pressed against the surface 25a of the topmost sheet of paper, and the double-dotted chained lineindicates a state in which only the half-circumferential face 34 a ofthe half-moon roller 34 is pressed against the surface 25 a of thetopmost sheet of paper.

As is clear from FIG. 6, before the auxiliary roller 36 is separatedfrom the surface 25 a of the topmost sheet of paper, the one end 34 b,which has a large curvature R, of the half-circumferential face 34 a ispressed against the surface 25 a of the topmost sheet of paper.

Then, the half-moon roller 34 further rotates so that thehalf-circumferential face 34 a on the left side from the position 34 ppresses against the surface 25 a of the topmost sheet of paper, anduntil the auxiliary roller 36 separates from the surface 25 a of thetopmost sheet of paper, the one end 34 b, which has a large curvature R,of the half-circumferential face 34 a continues to press against thesurface 25 a of the topmost sheet of paper.

Accordingly, for a predetermined period before the auxiliary roller 36separates from the surface 25 a of the topmost sheet of paper, the oneend 34 b, which has a large curvature R, of the half-circumferentialface 34 a continues to press against the surface 25 a of the topmostsheet of paper.

While the one end 34 b, which has a large curvature R, of thehalf-circumferential face 34 a continues to press against the surface ofthe topmost sheet of paper, the auxiliary roller 36 also is pressingagainst the surface of the topmost sheet of paper, so the contact areaof the half-circumferential face 34 a and the auxiliary roller 36 withthe surface of the topmost sheet of paper increases, and the springrestoring force that pushes up the paper batch on the bottom plate 31 isdispersed, and thus the contact force of the one end 34 b of thehalf-circumferential face 34 a against the surface of the topmost sheetof paper decreases. Therefore, the static frictional force between thetopmost sheet of paper and the sheet of paper below the topmost sheet ofpaper decreases, so the topmost sheet of paper is easily pulled awayfrom the sheet of paper below by the one end 34 b of thehalf-circumferential face 34 a, and thus conveyance of the topmost sheetof paper starts quickly. Immediately after the start of conveyance, onlya smaller kinetic frictional force occurs between the topmost sheet ofpaper and the sheet of paper below the topmost sheet of paper, sopulling out of the topmost sheet of paper by the half-circumferentialface 34 a of the half-moon roller 34 is reliably continued. As a result,only the topmost sheet of paper is pulled out, and paper multi-feedingdoes not occur.

Above, a preferred embodiment of the invention was described withreference to the attached figures, but of course the invention is notlimited by that example. It will be clear to a person having ordinaryskill in the art that within the category described in the claims,various modified or revised examples can be arrived at, and it will beunderstood by a person having ordinary skill in the art that that suchexamples also are naturally encompassed by the technical scope of theinvention.

For example, the extent to which the curvature R of the one end 34 b ofthe half-moon roller 34 increases may be appropriately changed. Also,the invention is applicable not only to a paper feed tray that storesprinting paper in a stacked manner, but also to an original tray thatstores original paper in a stacked manner.

The present invention may be embodied in various other forms withoutdeparting from the spirit or essential characteristics thereof. Theembodiments disclosed in this application are to be considered in allrespects as illustrative and not limiting. The scope of the invention isindicated by the appended claims rather than by the foregoingdescription, and all modifications or changes that come within themeaning and range of equivalency of the claims are intended to beembraced therein.

1. A paper feed apparatus having a half-moon roller disposed above aplurality of sheets of paper stored in a stacked manner, and anauxiliary roller provided along one end of a half-circumferential faceof the half-moon roller, the half-moon roller being rotated in a statein which a topmost sheet of paper has been put in contact with a heightregulating member due to the sheets of paper being biased upward, sothat the auxiliary roller and the half-circumferential face of thehalf-moon roller are successively pushed against the topmost sheet ofpaper, and while the sheets of paper are pushed down by the auxiliaryroller or the half-circumferential face of the half-moon roller, thetopmost sheet of paper is pulled out by the half-circumferential face ofthe half-moon roller: the one end of the half-circumferential face ofthe half-moon roller being separated from the auxiliary roller, and acurvature of the one end of the half-circumferential face beinggradually increased closer to the auxiliary roller.
 2. The paper feedapparatus according to claim 1, wherein before the auxiliary rollerseparates from the surface of the topmost sheet of paper, the one end ofthe half-circumferential face of the half-moon roller having a largecurvature presses against the surface of the topmost sheet of paper. 3.The paper feed apparatus according to claim 1, wherein thehalf-circumferential face of the half-moon roller comprises a frictionalface.
 4. The paper feed apparatus according to claim 1, wherein thehalf-moon roller comprises a frame body that has been fixed to a shaftthat serves as a rotational center of the half-moon roller, and afriction rubber that has been overlaid on the half-circumferential faceof the frame body, the auxiliary roller being rotatably linked to oneend of the frame body, and the half-circumferential face of thehalf-moon roller is the outside surface of the friction rubber, and theone end of the half-circumferential face of the half-moon roller is partof the friction rubber.